I have about 10 different files going by the name js3250.dll, but they all say version 4.0 in file properties (but a few of them don't have a version tab in file properties). File dates range from 2/19/2008 to 7/19/2012. File size ranges from 443 kb to 1016 kb. They are associated with FF 2.0.0.2x, Navigator 9.0, and a couple different versions of Palemoon.

Are they interchangeable? Is there a "best" version (in terms of stability, performance) to be running on a win-98 system for FF 2.0.0.2x ?

I have them in my HP Deskjet, K-Meleon, Palemoon, and Firefox folders. Dates range from 10/15/2001 to 9/12/2011. I also have one I built myself from the Firefox 2 sources two months ago (it doesn't work ).

>they all say version 4.0

Yup.

>Are they interchangeable?

Nope.

Use Dependency Walker (or any PE viewer) to see the API differences in the Exports sections. IIRC, the API was changed dramatically for FF3 and has continued to evolve slowly since then. See attachment for Palemoon 2.0 and 3.6 API listings (courtesy of DW).

That said, for FF3 and later it might be possible to use slightly later versions. And it also might be possible to create a wrapper that includes all APIs, forwarding to the most recent version of each. Because source code is available, it should be possible to determine compatibility.

Palemoon JS3250 APIs.7z