I and another developer are working on the same VS 2008 project using Source Safe. If one of us needs to add a new item, the person who doesn't have the csproj file checked out gets a message that they can't add because csproj and vspscc files are checked out.
Is this the normal behavior of Source Safe? What's the workaround beside asking the person to check in or to use another source control software?
That was 'normal behavior' back when I used VSS in 200-2006 time frame. There might be some options in VSS to turn off "exclusive checkout" which would let both of you check out the file at the same time, and whoever checks it in 2nd has to do a merge.
You can turn off exclusive checkout in SourceSafe via the Options dialog, Allow Multiple Checkouts checkbox. This will allow you and your co-worker to both have the .csproj checked out at the same time. However, if you both make changes, you will need to merge those changes when the second person does their check-in -- and SourceSafe has notoriously weak merge tools compared to other version control systems. So although multiple checkout can be a lifesaver, you'll still want to avoid it where possible.