Only from the videos I could find, this is a duplication glitch, in which case you are NOT allowed to make a infinite lava source. For specification, if you produce any item unnaturally via redstone which you shouldn’t be able to (like for example lava in this case) then it is banned.

I have watched a video also ‘claiming to make one’ and it is infact a joke:

Eitherway, thanks for asking. I’m not going to shut this as if anyone DOES know how to make one without a glitch, or you can link the respective video your referencing, we can gladly moderate the video and see if the ‘infinite lava’ production is not an abuse of the mechanics- and even then it might be banned.