Hi,
It is theoretically possible but I have never tried it and it is possible it won't work well.
It would require a reference to mojoPortal.Web.dll and it would also require that the mojoPortal.Business.dll, and mojoPortal.Data.dll exist in the bin folder and that you have the mojoportal connection string in the appSettings of your custom app.
Maybe it can work, I don't know for sure.
Hope it helps,
Joe