I hit the following error trying to install SOA 184.108.40.206 on a Linux x86-64 environment. It seems a few people have hit this issue so I thought I would post the solution I found. Its not much of a "fix", but while researching the problem I noticed some questionable suggestions, including deleting files. Who knows, they may have opened an SR and thats what they were told to do. Regardless, here is what worked for me.
On the Select Domain Source screen:
I would get the following error when trying to select “Oracle SOA Suite”
The solution I found, was just to select the products you want from the bottom up. So Oracle JRF first, Oracle WSM Policy Manager second, etc. By looking at error above you can see that there are multiple dependencies, one such being Oracle WSM Policy Manager. So if you select them first, you don't get the error.
If your using windows try running the config.cmd script as an Administrator.