Yes, you can run OS X 10.5 as a Guest. If your Mac is 10.11, you should be using Fusion 8.
Fusion as well as Fusion Pro will work fine. Likely, you only need Fusion (non-Pro).
An important clarification is required: Prior to OS X 10.7 (Lion), the Apple Software License Agreement only allows Server versions of Mac OS X to be run in a virtual machine, so you'd need to ensure that you have Mac OS X 10.5 Server (or Mac OS X 10.6 Server).
Apple had been selling Mac OS X 10.6 Server for something like $30 through their telephone sales center only (not available online)... there are other threads here in the forum with the details. That Mac OS X 10.6 Server pack is perfect for running PowerPC apps in a VM.
Great information, thank you!
I run both Mac OS X 10.5 Server (Leopard) and Mac OS X 10.6 Server (Snow Leopard) in virtual machines under VMware Fusion 8, running on OS X 10.11 (El Capitan). They both work fine. I have had those virtual machines for a long time - I upgraded both OS X (host) and VMware Fusion several times, keeping the same virtual machines.
You can buy Mac OS X 10.6 Server (Snow Leopard) from Apple for just under $20 if you are in the US. Call Apple Sales. It may take more than one try to find someone at Apple who knows how to place the order for you. Persistence pays off. Be careful - Apple's website sells Snow Leopard (not Snow Leopard Server). The non-Server version will not run on VMware Fusion or Parallels.
Snow Leopard Server runs the same as Snow Leopard (non-Server) - just ignore the Server application.
Thank you, I appreciate it!