What source licenses allow inclusion in commercial applications

Question

Which open source licenses allows inclusion of the licensed source code in commercial applications without having to make our program open source as well?

In particular, I was looking on koders.com for an implementation of a fast hash algorithm in C#, but I am not sure if Iam allowed to use it in a commerial application without limits.

EDIT:

/// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.

Answer 1

Very few don't. Even the much-maligned GPL allows inclusion in commercial apps. But, you're probably looking for something in the LGPL, BSD, or MIT vein.

Answer 2

In licenses that enforce copyleft, that is, require the license of your program to be at least as liberal as that license itself, the rule is only enforced if you distribute your program. If your program is to stay in-house, you can use whatever you want with it. It's only if you wish to sell your application that the GPL would not allow it, and require distribution to be open-source.

Take with a grain of salt, as 1) I'm no lawyer, and 2) I believe this particular viewpoint is contested by some, but what I've seen suggests that this is the majority opinion.

Answer 3

I am not sure if Iam allowed to use it in a commerial application without limits

Most open source licenses are redistribution licenses, which means use isn't generally affected (or asserted to be affected) while (re)distribution is only permitted if certain requirements are met.

For example, the MIT license requires that its copyright be preserved. Most open source licenses have a similar requirement (including the BSD licenses). This means that wherever your program displays its copyright, it needs to additionally display the copyrights of any code you've lifted. If you do not do this, you do not have the right to redistribute your code (with the embedded MIT-licensed code).

The GPL is notable in that it additionally requires that your software be redistributable under the terms of the GPL. This means using GPL-licensed code, and redistributing your program, essentially makes your program GPL. The high-quality of some GPL programs has been successfully used to "free" previously non-free software.

There are some subtleties I'm glazing over here, but the answer you need is probably: ask the author of the code snippet. If this is impossible or impractical, ask a lawyer who is well-versed in copyright law, and especially familiar with software.

Answer 4

The mandate I've gotten from our company lawyers is basically this:

Web based: Open source is fine since it's not being redistributed.

Desktop App: No open source libs as it could force us to open our source.

In this same line of thought, if you are using 3rd party libraries, make sure to double check what libraries they're dependent on. We've come across a few commercial libraries that we considered using only to decide against it when we found that they were using open source libraries.

As mentioned, there are plenty of closed source apps that use open source libraries, so clearly there is some interpretation. No one is going to be able to get you to open your source code without a legal battle, so it may come down to how risk adverse you are.

Answer 5

The license part you showed is typical GPL. Therefore, if you use this code, your application must be released as open source, and must be released under GPL.

There are workarounds. For example, only build a small executable that includes this GPL code, and release this utility under GPL.

Other parts of your application can use "inter process communication" with this utility to consume its service. Then such parts do not need to be released as open source.

Answer 6

Those restrictions as mentioned by roto basically apply only to the GPL and very similar licenses. The Apache license (for example) doesn't require you to distribute your own product that uses an Apache licenced library as open source. Nor does the LGPL (unless you modify that library, in which case those specific modifications only must be distributed under the LGPL, not the entire application that uses the so-modified library). And then there's the GPL library exception used in for example the JDK, which allows the use of the binaries without releasing your product under the GPL but not the source.

For myself, I won't touch GPL licensed sourcecode with a 10ft pole unless on a machine that will never be used to create software for external distribution (and I do have a separate computer for things like that) so as to prevent the smallest possibility of accidental cross pollination of my own code with any GPL licensed code fragments.

But IANAL and happily so :)