Mine is working from email not the browser. Try emailing yourself that link and opening it in an email (it shouldn't go anywhere or open a new card). I have to click it a few times until it turns grey and highlighted and wait about 20 seconds and then the app shows up in my launcher.
Be sure you copy the entire link because the forum truncates this link:
http://cdn.downloads.palm.com/apps/3...all_signed.ipk
That will tell me if it's the mods in the email app I've made or if this is possible with unmodified code. If it's the mods I've done to my email app, I will share those but it's better to test unmodified first.