There are some non-English dictionaries listing the word "naďve" (notice the ď) as an existing English word, apparently synonymic to naive. Is this a real English word? If so, how did it receive its spelling?
The word "naďve" is a misspelling of "naïve" caused by a computer error. Written this way, it is not a part of English (nor French) meaning naïve, nor an attempt at writing "native".
When a text is stored in a computer, an encoding is always used to convert the characters from the text to their associated numbers (code points), traditionally saved as bytes. However, when the specific encoding is not stored together with the character data (quite commonly), the text may become partially garbled when viewed with a different encoding than the one that was used to save the file. This effect is known as mojibake.
Though the use of Unicode has got us rid of most of these errors, some may still be found, especially in texts on older websites or databases. Plain English characters (Latin without accents or diacritics) are shared across large number of encodings and don't require special conversion. However, regional letters like ï, é etc. may become replaced with completely unrelated ones.
'ï' (LATIN SMALL LETTER I WITH DIAERESIS) has an associated code point 239 in Windows-1252 and Latin-1, two encodings commonly used for English and Western European languages. However, encodings Windows-1250 and Latin-2, used for Central European languages, also define the code point 239, but with an associated character 'ď' (LATIN SMALL LETTER D WITH CARON). Thus all occurences of 'ï' can get replaced with 'ď'.
There aren't many other occurences of this error for other words, because Windows-1250 and Windows-1252 share a fair number of same code points, making "naďve" the most common word affected by this error. "naďf" is also affected. Examples from other encodings are "naяve" (Windows-1251) and "naοve" (omicron, Windows-1253). Cyrillic and Greek encodings don't share any accented Latin letters, so all foreign English words are affected there. The funnier examples include "dejŕ vu", "ĺngström" (from ångström), "medićval" (from mediæval), "caffč", and even "ţorn" (from þorn). In Russian, "Zoл" is produced from Zoë.
It's interesting to see how a computer error could have almost created a new word, if it weren't for Unicode to stop the confusion of tongues.