I find it very strange as we (the dev team) pretty much use the source build (and DNN_Platform.sln solution) exclusively (it's QA who make more use of the install/upgrade packages). I dont understand why you're seeing anything different, are you perhaps using an old (vs.net 2010/2012) version of visual studio?

Here's my standard process for working with source builds (many people automate these steps with powershell scripts but i'll show the manual steps)

1. I check out the branch I want from github

2. I execute the following commands to ensure a clean environment (which can be necessary when switched from 7.4.2 to 8.0.0 etc)

• git reset --hard
• git clean -dfx

3. I open vs.net 2013/2015 and open the DNN_Platform.sln solution

4 I change the drop-down to release and right-click the solution file at the top and do a "rebuild solution" (typically a build solution is fine for a "fresh" build but a little paranoia never hurts)

5. I hit localhost/dnn_platform and everything works

Note: if i'm debugging i'll change the web.config to use debug

As to the missing appSetting this is deliberate - Joe covered this in a recent blog http://www.dnnsoftware.com/community-blog/cid/155269/a-break-with-the-past , and i've ensured it was noted on the DNN 8 breaking changes wiki http://www.dnnsoftware.com/wiki/dnn-8-breaking-changes