According to GitHub, the first commit to infinity-next was April 21 (https://github.com/infinity-next/infinity-next/commits/master?page=32). HW was donated 15 BTC on May 6, and HW announced that he had selected Next on May 20 (https://archive.is/wmYNv). If Josh started on Next before HW had the financial means to pay him, then I would agree that Josh owns Next and 8chan funded the development of his project.
As for why HW won't use it: Jim and HW want to put non-free software into Next, which is probably in violation of the AGPL. Instead of risking Josh suing them, they tried to get the code relicensed under GPL. The reason that Josh has asserted that GPL is closed source is that, under the GPL, 8chan doesn't have to release the software the the site is actually running on, because it isn't being distributing per the definition of distribution in the GPL. The AGPL was designed such that a website has to release the source that is actually running the site. And that is why Josh wants to hold them to the AGPL: Softserve and Ronin Pass (money making schemes) are both closed-source.
The funniest thing about the DebugBar IP leak thing is that he had done it on numerous occasions on infinitydev.org.
Sorry I didn't capture the time with this, but the last modified date on the September 7th. I screencapped it to ask about on >>>/next/.