Adding LP solvers to release containers is issue923, so let's close this issue.

According to the issue title it is. But in the story of the sprint to which this issue (task?) belongs, we also wanted to find out how we can use SoPlex in release containers. I don't know if this task/issue should also be about this or not. At least I wouldn't vote for having another issue on the issue tracker for this because I don't think having so many issues that won't add any code to Fast Downward are useful/necessary.

I sent our GitHub Actions prototype for SoPlex to the ZIB license folks and they answered that our approach is ok.

If this issue is only about *finding* a way to run SoPlex, I think we can close it.

> PS: why do we have 3 separate issues now for each LP solver

I thought it would help to untangle the discussion. Each solver has a different license and so there are different requirements of what we need to do to run it as a github action. For example, the solution we have here is not a solution for CPLEX or Gurobi as far as I know.

> why are they meta issues? 

I messed that up. I was thinking of the keyword "meta" that we renamed to "infrastructure" a while ago to avoid exactly this confusion.

Adding soplex to the existing github actions prototype (issue94) was easy and is working on ubuntu (not tested on other Windows or Mac because there are other issues that prevent running the full test suites there).

PS: why do we have 3 separate issues now for each LP solver and why are they meta issues? I think dealing with all this in issue940 would be fine.

SoPlex (and SCIP) are published under the ZIB license:
https://www.scipopt.org/academic.txt

Point 3 is relevant for us: 

    You may copy and distribute the Program or work based on the Program
    in source, object, or executable form provided that you also meet all
    of the following conditions:

Conditions a, b, and c only refer to modifying, distributing, or publishing the code. Condition d is that we have to include the source code. All of this should be fine if SoPlex cannot be extracted from the Github action, i.e., if there is no way to get to the SoPlex source code from a public account. In that case, we are neither distributing nor publishing the code. Copying and using the code on an external machine is not a problem.

If on the other hand, the SoPlex source code is publicly accessible, this would count as a distribution and we would have to offer this “package” under the ZIB license which includes tracking access to it.

One way we discussed was to download the SoPlex source code from an encrypted URL, stored as a "Secret" for the Github action. For this issue, we should build a prototype of this interaction.