The classic ISA bus has very little need for bus termination. For example the first IBM PCs, such as the PC, XT and AT for example did not use any bus termination, and their ISA bus worked fine.
So, in short the answer is, no you don't have to terminate the bus, as depending on how you do it, it might just make things worse. The cards on the bus are definitely not designed to sit in a system that has DC or AC terminations, so for example they might have trouble driving a terminated data bus, due to more DC current it takes to drive it, or due to the increased capacitance of AC termination.
The reason why it can work without termination is strictly the speed it operates. Not the clock speed that can be measured in MHz, but the speed of the logic signal edges. The used logic chips of the computers mentioned above are LS TTL or ALS TTL types, which on a properly designed backplane PCB will not cause too much trouble. Some overshoot and undershoot may be present and that is fine as long as it does not cause ringing.
The "some homebrew projects use active termination" is what they chose to do. One of the projects seem to work better with it, but it did mix faster F series TTL chips with ALS TTL chips, so faster chips mean it is harder to make it more reliable, and the PCB was only two-sided, instead of having four layers to include reference planes for the signals, so crosstalk can be an issue. So, a good desing might require termination to work, a better design doesn't require termination to work.