As OpenD6 is a bit older (2009 while the ogl used is from 2000) there was probably no thought about the recent trend of digitalization and usage of RPG rules in computer games. So I'm wondering there. If I create an RPG system using OpenD6 am I then also allowed to use that system in a computer game according to the OGL (reading through the OGL a few times which is in essence the Wizards of the Coast OGL... I'm not 100% there)?
I will talk to the 5e OGL portion, as I don't know much about D6. You may under OGL use SRD content in a computer game, but the files where the SRD content reside must be released under the OGL as derivative work.
While the D6 doesn't talk about software, it should be the same case -- those files which contain open material would be derivative and have to be open under the same license. While the license doesn't mention the method of distrobution, the license doesn't forbid software usage (which I know some between version of the OGL did).
I am not a lawyer and this is not legal advice. When in doubt, contact a lawyer versed in copyright law.