Is Pale Moon up-to-date?
Yes, it certainly is.
Pale Moon is actively developed. The confusion is apparently present because Pale Moon has a lower major version number than its sibling Firefox.
A few points:
- Security: Pale Moon is kept updated with the latest applicable security patches that make it into the Mozilla (Firefox/seamonkey/thunderbird/etc.) source code.
- Version numbers: Pale Moon's version number is what it is because of the version of Firefox it is most compatible with. e.g.: Pale Moon 24.6 is a far cry from Firefox 24.0 in terms of code, and should not be compared with it. It just means that the front-end code is most compatible with Firefox 24 from an add-on point of view.
- Feature updates: Pale Moon adopts a number of features from later Firefox versions that are considered essential and desired for Pale Moon
- Divergence: Pale Moon increasingly diverts from what Mozilla is doing to Firefox, and going in its own direction. Versioning of Pale Moon can therefore seem a little confusing since it originally was a fairly close reflection of Firefox with the same version, but it no longer is (and hasn't been for a while).
Version numbers should therefore not be compared to Firefox versions at this point. Firefox's arbitrary, calendar-ruled versioning is a poor reflection of the state of code and state of features.