Split license files for better recognition

[msujew]

What it does

GitHub is using licensee to identify license information in repositories. The project identifies licenses on a per file basis and therefore has trouble with our double-license-in-one-file format.

I've split the LICENSE file into LICENSE-GPL and LICENSE-EPL, so that GitHub can correctly identify them. See this test repo where GitHub is able to successfully identify the two used licenses.

How to test

Merge this PR and assert that the license information in the repository is correctly updated.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[marcdumais-work]

LGTM, thanks Mark!

[SpessartZiegler]

@msujew : In the file LICENSE (version 1.36.0) the was the GPL-2.0-with-classpath-exception (see line 625 ff). Now you split it. This is fine. But you copied a special classpath exception to LICENSE-GPL (see line 343 ff). Why did you add a special license from Oracle to Theia? I have searched and only in this file the name ORACLE appears.

Maybe you should replace this text by the original one from spdx.org and use the SPDX shot identifier GPL-2.0-with-classpath-exception for this.

[marcdumais-work]

Thank you @SpessartZiegler - it's indeed wrong to have "GPL-2.0" detected for this repo. I will look into your suggestions!

[marcdumais-work]

@msujew I think we may have the root cause of the GitHub license detection issue: #12424 (comment) . The SPDX we've been using in various package.json files, for the secondary license, is not correct. It's also incorrect in all our source code header files, and the license name is mentioned wrong in many .md files. As also noticed by @SpessartZiegler, the text of our "GNU General Public License v2.0 w/Classpath exception" text has changed during the split, now looking like one that was customized by Oracle (contains an extra Oracle-specific paragraph).

I will open an issue about this.

[marcdumais-work]

PR #12584

[marcdumais-work]

Thank you @SpessartZiegler - it's indeed wrong to have "GPL-2.0" detected for this repo. I will look into your suggestions!

update:
Now that I investigated this a bit deeper, I no longer think that it's necessarily wrong for GitHub to report "GPL-2.0" as a detected license. It's technically correct. I guess I hoped GitHub would detect [1] the exact "with classpath exception" variant of the license, but it does not and it's probably ok. (i.e. the detected license list is not the whole story, just a teaser)

[1]: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository#detecting-a-license