On the license question: https://marc.info/?l=xalan-j-users&m=164993354220907&w=2 I haven't received a reply that answered the question. The only reply was: Joseph Kesselman : > It has been a long time since I looked at this, I believe IntStack > was official JDK code but deprecated. Since we were still depending > upon it it we copied it into Xalan's source. Web search finds a > version on GitHub which says its performance was several times > better than the then-available alternatives. but this doesn't really answer the question ... Anyway, IIUC, except for maybe the license thing, things should be ready: Latest patch (IIUC): https://issues.guix.gnu.org/32947#29