If I play the event Modded and the item I am installing only costs one, do I get two credits?

Second, can you have two of the same card on the board at the same time, like Akamatsu Mem Chip or access to Global Security?

1) No

2) Yes

To add to ngunz answer, you may have multiples of a card unless the card is unique (such as Aesop's pawnshop or Wyldside). Unique cards are identified by a diamond before the name.

There is usually no benefit to having multiples of the same program in play (with some exceptions such as djinn or sahasrara).

To add to ngunz answer, you may have multiples of a card unless the card is unique (such as Aesop's pawnshop or Wyldside). Unique cards are identified by a diamond before the name.

There is usually no benefit to having multiples of the same program in play (with some exceptions such as djinn or sahasrara).

as long as you remember the caveat with sahasrara that you can't spend it's recurring credits on any program that would cause it to be overwritten.

Indeed. Having two down is only useful to get more expensive programs into play while you have the spare MU for them. Once you're at your MU limit (or have no more programs worth installing) they don't really do anything probably worth Scavenging your Sahasraras away when you're putting the last programs into play.