Depends. You'd certainly see an ever-growing item in the assets area of the balance sheet, probably labelled intellectual property. Other than that, all you'd see in the P&L is that salaries are lower than they should be (pretty much impossible to detect).
The other reliable indicator, IMO, is to check the amount of tax paid. If they're claiming $X million profit and they're not paying pretty close to X*0.3 in tax expense, then something is not right (*). Cashflow statement would be another good place to look.
Just to clarify, it's usually ok for there to be a difference between reported profit and cashflow because that's where your capital expenditure comes out. With a trucking company, that's where you pay for your new truck. The difference with software companies is that most R&D is wasted and has no residual value. The trucking company has a truck it can point at, use and even sell. The software company just has salaries it's paid out, and maybe a relatively small amount of code that will have some use going forward.
(*) the other valid reason for a reduced taxation rate is the claiming of the R&D tax incentive, which is a good thing. Tanstaafl, however, because the R&D concession ultimately means the company runs out of franking credits earlier.