Hi @RedMan - see here: https://business.gov.au/grants-and-programs/pooled-development-funds

This scheme is now closed to new applicants (i.e. new companies), however those companies who are already in it can stay in it for as long as they are eligible, and their shareholders can benefit from favourable tax treatment during this time.  My understanding was that it was originally set-up to encourage investment in start-ups that had a heavy emphasis on R&D, so like a R&D incentive, but ongoing.  I'm not sure that all participants ended up being R&D heavy, but certainly a lot of the earlier ones did.  The government explain it like this:

Overview

The aim of the Pooled Development Funds programme was to increase the supply of capital to Australian small and medium-size enterprises (SMEs).

PDFs are venture capital funds registered under the Pooled Development Funds Act 1992

PDFs and their shareholders receive tax benefits on the income derived from their equity investments. This is to help compensate for the higher risk of investing in SMEs.

PDFs will be taxed at 15% on the income and gains derived from equity investments in Australian SMEs. Shareholders are exempt from tax on the income and gains derived from holding and disposing of PDF shares.  

[Bear77 note: In other words, no tax on distributions or dividends, and no tax on capital gains when you sell.  The flip-side of that is that if you sell at a loss, there is no capital loss to be offset against other gains made elsewhere.  Capital gains and losses do not apply to PDFs.]

The extent of the above tax benefits depends upon a number of factors. PDFs and their shareholders should seek professional tax advice.

For a list of companies that are registered as PDF's, see here:  https://business.gov.au/grants-and-programs/pooled-development-funds/list-of-pooled-development-funds

[Bear77 note: I was invested in Acrux a few years back before they got torpedoed by the FDA deciding that their drug was only suitable for a much smaller subset of their planned target market, so I have experienced investing in a PDF first-hand.  The only drawback I found was not being able to claim the capital loss on disposal.  If you make a capital gain instead, there's probably no downside.]