The Apache Software Foundation hosts many projects, of which httpd is probably the best known. If you refer to that: there is no (released) Apache httpd 2.5. The latest release is 2.4.58. Source is here.
Where can I get the source code to build Apache 2.5 for Red Hat 8 ? The links on apache.org redirect to the source for Apache 2.4, and I don’t see any packages for Apache 2.5 in the Red Hat repos.