In these boards it's not "5V tolerant". It's actual 5V I/O. EPF10K70. They are obsolete, and so the production part doesn't apply. Solely for hobby stuff.
What's the software requirement side look like? Intel's website[1; under Legacy Devices] says Quartus II v9.0 was the latest release that could target FLEX 10K devices. Doesn't look like you can download that release anymore, and liable to run into compatibility issues just installing on modern OSs without a VM.
Bummer, and a real shame given how seemingly common regressions are in this space. Not my specialization, but anecdotally over a decade or so, I've encountered scenarios on MAX 7000 and Cyclone II (Quartus II v9.0 builds, v10.x breaks), Virtex-7 (Vivado v2018.3 builds, v2019.1 breaks) and Virtex-5 (ISE v14.6 builds, v14.7 breaks).