Umm, much easier than editing SQL databases, just go to Menu > Settings > Applications > and tick 'Unknown sources'.
AT&T removed that dialog. That is not even visible on the Captivate.
Go into sqlite3 database settings.db look at table security & do an update on row 6. Set the Boolean to 1. Works for me guaranteed 100% to side load apps with astros manager, email attachment, drop box or even with SAM.
You need to copy the db out of the phone, edit on your pc and copy it back to the phone.
Here, this is how I do it:
I go into adb shell, su
1) Copy the /dbdata/databases/com.android.providers.settings/settings.db to my sdcard,
2) make a backup of it.
3) adb pull the file from my sdcard to my mac desktop.
4) fire up sqlite3 (use whatever tool you want. I do it in the command line).
5) look for secure table. select it. Row 6 will have what you need.
6) Update the row:
update secure set value = 1 where _id=6
7) Save out the settings.db
8) adb push it back to the phone.
run in adb shell/su :
busybox cp /sdcard/settings.db /dbdata/databases/com.android.providers.settings
9) set the permissions back
chmod 777 /dbdata/databases/com.android.providers.settings/settings.db
10) reboot (in adb)
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Advice given by an illiterate iPhone 4 owner.