Possible GPL issue with PhysX

PaladinOfKaos · **Joined:** Thu Aug 03, 2006 10:55 pm **Posts:** 625

I noticed that Cyan's GPL doesn't include an exception for linking to PhysX. This would make distributing any builds in violation of the GPL.

Normally "system libraries" aren't considered for GPL requirements (so you can link a GPL program against Microsoft's C runtime with no issues), but higher-level libraries such as PhysX are typically required to be GPL to be linked with GPL code. Obviously PhysX won't be going GPL any time soon, so an exception is the best option.

IANAL, I've just spent enough time around the GPL to know how it generally works (or at least how it's usually applied in practice).

I've already sent an email to Cyan legal about this (I assume they meant to add an exception), so hopefully it will be cleared up soon. I just wanted to give everyone a heads up about the potential issue.

D'raekmus · **Joined:** Sat Nov 29, 2008 2:47 am **Posts:** 35

Huh... I take it, Paladin, that the client might be altered to run with Bullet Physics? Possibly merging your Plasmaclient with CWE?

I have no comprehension of programming (very little, casual playing around), so I don't know how difficult it would be making this conversion. However, I guess the first step would be to make wrappers to run PhysX calls on Bullet, gradually replacing parts of the PhysX code with Bullet physics.

But, as I said, I really don't know about programming.

Frankly, from what I've seen of Bullet, it seems to blast PhysX out of the water. (No pun intended)

So, AFAIU, devs will have to implement an alternative physics engine?

Nye_Sigismund · **Posted:** Tue Apr 12, 2011 6:04 pm

D'raekmus wrote:

So, AFAIU, devs will have to implement an alternative physics engine?

Certainly the GoW branch is looking to do this.

PaladinOfKaos · **Joined:** Thu Aug 03, 2006 10:55 pm **Posts:** 625

We're going to have to port to something else anyway, for cross-platform compatibility. But yes, unless Cyan legal clears this up it has the potential to cause problems.

Nalates · **Posted:** Tue Apr 12, 2011 9:31 pm

Mac_Fife looked into the issue over at OU. PhysX does not lend itself to GPL licensing. That is a problem when one wants to distribute a binary of the CWE. If one just wants to roll their own for private use, not so much. But, how many of us want to be compiling our own copies?

I expect we will see PhysX taken out and something used in it's place, ODE, Bullet... something. As well as DirectX.

D'raekmus · **Joined:** Sat Nov 29, 2008 2:47 am **Posts:** 35

Well, if we ever do this kind of stuff, could we have a documentation listing how to build Uru with a particular Physics library?

A program I came across a while back, Irrlicht, I believe, is a high-quality rendering engine, that uses a variety of different physics engines through scripts and wrappers, I think.

cjkelly1 · **Joined:** Tue May 09, 2006 7:48 pm **Posts:** 100

OpenSSL has licensing questions as well.

Free Software Foundation wrote:

The license of OpenSSL is a conjunction of two licenses, one of them being the license of SSLeay. You must follow both. The combination results in a copyleft free software license that is incompatible with the GNU GPL. It also has an advertising clause like the original BSD license and the Apache license.

http://www.gnu.org/licenses/license-list.html

There are various thoughts on this topic. Some say that dynamic linking is okay, some say that an exemption will do the trick, and some say just use GnuTLS and avoid the whole problem. Unfortunately, I am not a licensing expert so I cannot offer an informed opinion on this issue.

Lontahv · **Joined:** Sat Apr 14, 2007 9:51 pm **Posts:** 265

D'raekmus wrote:

Well, if we ever do this kind of stuff, could we have a documentation listing how to build Uru with a particular Physics library?

A program I came across a while back, Irrlicht, I believe, is a high-quality rendering engine, that uses a variety of different physics engines through scripts and wrappers, I think.

Plasma's data structure and layout makes this kind of flexibility complicated so say the least. I think that if a branch of Uru wants to implement Bullet, it should be fully replace PhysX. However, I'm getting a little off topic here.

Cyan will (most likely) be able to make an exception so that they can include PhysX. However, I don't believe this means that people can distribute PhysX dynamic libraries with a compilation of the engine. Most likely people will have to go to the PhysX website and manually install the libraries needed to run the game.

Marten · **Posted:** Wed Apr 13, 2011 1:28 am

cjkelly1 wrote:

OpenSSL has licensing questions as well.

There are various thoughts on this topic. Some say that dynamic linking is okay, some say that an exemption will do the trick, and some say just use GnuTLS and avoid the whole problem. Unfortunately, I am not a licensing expert so I cannot offer an informed opinion on this issue.

According to OpenSSL.org, this issue could be resolved (more simply) with an exception, much like the PhysX issue.

Reference: http://openssl.org/support/faq.html#LEGAL2

D'raekmus · **Joined:** Sat Nov 29, 2008 2:47 am **Posts:** 35

Marten wrote:

cjkelly1 wrote:

OpenSSL has licensing questions as well.

There are various thoughts on this topic. Some say that dynamic linking is okay, some say that an exemption will do the trick, and some say just use GnuTLS and avoid the whole problem. Unfortunately, I am not a licensing expert so I cannot offer an informed opinion on this issue.

According to OpenSSL.org, this issue could be resolved (more simply) with an exception, much like the PhysX issue.

Reference: http://openssl.org/support/faq.html#LEGAL2

Well, I believe that PhysX is used as a dependency, so it falls under the same use as DirectX.

Nvidia supposedly has PhysX binaries for Linux. Can anyone confirm this?

I think the first step, though, would be to get rid of dependency on DirectX, replace it with OpenGL and OpenSL, perhaps?

Marten · **Posted:** Wed Apr 13, 2011 3:16 am

D'raekmus wrote:

Well, I believe that PhysX is used as a dependency, so it falls under the same use as DirectX.

Nvidia supposedly has PhysX binaries for Linux. Can anyone confirm this?

I think the first step, though, would be to get rid of dependency on DirectX, replace it with OpenGL and OpenSL, perhaps?

I believe the initial intent of this discussion is to talk about licensing issues, not dependency issues.

The licensing issue for PhysX seems to affect all platforms for which PhysX is available.

The licensing issue for OpenSSL affects platforms where OpenSSL is not a default part of the operating system (on Linux, it is not an issue).

There is no licensing issue with DirectX for the platforms where it is available.

MustardJeep · **Posted:** Tue May 03, 2011 4:11 pm

physx is 100% free for commercial and non commercial, as long as the physx libs are dynamically linked and loaded there is no issue I can see with the gpl and physx license. If your wanting the end all answer however just shoot the physx license guys a email they will be happy to tell you exactly how to stay within the letter of the license.

AdamJohnso · **Posted:** Tue May 03, 2011 4:31 pm

MustardJeep wrote:

physx is 100% free for commercial and non commercial, as long as the physx libs are dynamically linked and loaded there is no issue I can see with the gpl and physx license. If your wanting the end all answer however just shoot the physx license guys a email they will be happy to tell you exactly how to stay within the letter of the license.

No. The GPL is viral. Without an exception, the GPL will cover the PhysX code, which nvidia states on their website is not allowed. (Evidently, you did not read their website.)

JWPlatt · **Posted:** Tue May 03, 2011 5:53 pm

Both OpenUru.org and the GoW have sent their opinions on this matter to Cyan Legal. For our part, I first communicated with a representative of the Free Software Foundation who, after some discussion, could not provide an authoritative answer specifically about PhysX except that in the absence of clear permission, an exception is recommended. However, PhysX is not the only library affected by this question. The GPLv3 does have a somewhat ambiguous "out" when a library can be reasonable expected to be part of the OS. The question gets technical and I could find no precedent for or against PhysX, a free physics SDK with a liberal licence (the main constraint being that you must register and download it yourself for distributed builds), but it's not open source.

In the absence of a clear ruling or precedent, or exceptions in the Cyan license, these are some of the options: 1) Make everyone compile their own client and plugin - hardly workable, but legal. 2) Wait for Cyan exceptions in their license. 3) Develop for other libraries. 4) Go ahead and build for public release to draw attention and wait for legal complaints to test precedent for a clear ruling. The last option is clearly not preferred.

MustardJeep · **Posted:** Wed May 04, 2011 1:51 am

@ adam

Did, but this post is just to congratulate you. Eight years in I finally see a post of yours stating a bad opinion on the gpl.

Cheers!

On another note not that I've been Researching the applicable licenses for the last eight years in fear cyan would go gpl considering it's popularity with a certain "redacted" guild group when thing finally went os..... but

as long as a file is nominally a "library" free standing and separate a gpl program can make use of it but not "infect" it. So the easy answer is the same one as the moula data file repository. Use the moula install. take great pains in keeping the fan client versions in line with the current moula version of physx and it's possible.

simplistic maybe but it is arguably a faster approach then gutting physx out of the client or getting a better license from cyan.

ps jwplatt did you really expect the gpl guys to tell you a "official" way on how to bypass the gpl? :lol:

Possible GPL issue with PhysX

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