Whereas someone who reads the license agreement (like me) can assume it means we would violate the agreement by keeping multiple versions installed, it seems to be common sense and relatively common knowledge that we may keep multiple versions installed for testing. See the following thread:
The section that seems to not permit this practice is the following:
(h) Upgrades & Updates. If the Software is licensed as an upgrade or update, then you may only use the Software to replace a validly licensed version of the same software. You agree that the upgrade or update does not constitute the granting of a second license to the Software (i.e., you may not use the upgrade or update in addition to the software it is replacing, nor may you transfer the software which is being replaced to a third party).
Unless there is some other section or means that explicitly allows a licensee to keep multiple versions installed for testing,
the agreement should be edited to clearly and explicitly allow a licensee to keep multiple versions installed for testing,
perhaps limited to a single machine per license or whatever it takes to keep FMI comfortable with the agreement.