Official:

There are two different credit modifier calculated:
  	Ratio1 = Uploaded Total x 2 / Downloaded Total
  	Ratio2 = SQRT(Uploaded Total + 2)
Both ratios are compared and the lower value is used as modifier.
Some boundary conditions also exist:
  	> 	Uploaded Total < 1MB => Modifier = 1
  	> 	Downloaded Total = 0 => Modifier = 10
  	> 	The modifier may not be lower than 1 or higher than 10

lovelace:

dl-modifier=100*((1-1/(1+exp((3*{MB uploaded to us}^2-{MB downloaded from us}^2)/1000)))^6.6667)

new credit system (start:1, max:100, min:0.1, ratio:1:1.5, only one formula)
CreditThefts will not get any credits. Only clients using the 'SecureHash' are able to get a multiplier of 100. All others will stick at 10.

Pawcio:

 - Range from 1.0 to 100.0
- Multiplier of 3 (instead of 2) ---- ratio = 3 * downloaded / uploaded
- For new clients (downloaded and uploaded data less than 1MB) ratio = 3.0 (instead of 1.0)
- If you have recieved more than 1MB from someone but haven't given anything back user gets ratio = 100.0
- Small bonus for clients that have given you many MB:
- if you get 100MB then user recieve ratio = 50.0 till you give back 108MB
- 50MB - ratio = 25.0 - 55MB
- 25MB - ratio = 12.0 - 28MB
- 10MB - ratio = 5.0 - 12MB

Ratio:

EastShare:

  base ratings: id. users(100); not supported users(80); invalid id. users(0); min.=10, max.=5000
  +6 per MB uploaded and -2 for downloaded; +100 if upload 1MB+; if rating < 50 and upload 1MB+, rating = 50
