I’m wondering whether there are any known reasons that might prevent one from running RM9 and RM8 at the same time on a computer, or RM9 and RM7 ? I am primarily focused on OSX.
From a Windows perspective, there is no problem running all three pieces of software on the same machine at the same.
As far as running RM7 and RM8 together, there is no problem for the databases because your RM7 database is imported into RM8.
As far as running RM7 and RM9 together, there is no problem for the databases because your RM7 database is imported into RM9.
As far as running RM8 and RM9 together, you have to be careful about the databases. The reason is that RM9 converts your RM8 database to RM9 format at which point it can no longer be used by RM8. So if you want to have separate RM8 and RM9 databases, you have to make two copies of your RM8 database. One copy remains in RM8 format because you only open it with RM8. The other copy becomes your RM9 database as soon as you open it in RM9 and you can never us it in RM8 again.
All the RM7 database vs. RM8 database vs. RM9 database issues are identical between Windows and Mac. As far as the actual executable software, I suspect that you can have all three installed at the same time on a Mac, but a Mac person should be the one to give a reliable answer to that question.
Yes, on a Mac RM8 and RM9 are completely separate applications and so can both be used on the same Mac. However, as mentioned, it is important that they each use their own ‘data’ folders.